The present invention continues the development of a read/write recording apparatus for the data storage industry which development includes various components and assemblies described in the earlier issued patents and applications of which the applicant is the named inventor or co-inventor. These include U.S. Pat. No. 5,737,153 issued Apr. 7, 1998 directed to a positioning assembly for recording heads and electronic recording devices. In U.S. Pat. No. 5,777,823, a tape transport apparatus is described that incorporates porous air bearings, and this air bearing technology is extended in U.S. patent application Ser. No. 10/111,728, now U.S. Pat. No. 6,722,608 which claimed the priority of PCT/US99/25421 (published as WO 01/31648). Additional technologies for an overall system are identified in U.S. Pat. No. 6,078,478 and in U.S. patent application Ser. No. 10/486,492. now U.S. Pat. No. 6,876,512 which claimed the priority of PCT/US02/25037 (WO 03/015087).
As discussed in the background of the above-referenced patents and applications, the advent of the information age has experienced substantial growth in both the accumulation and storage of data for online usage as well as for archival purposes. While magnetic disc and optical storage systems have been developed to increase the density of data that can be stored and while other storage devices are contemplated, magnetic tape remains a highly desirable format. This is especially true where the ability to rapidly access the data is of less significance and cost is of concern. Magnetic tape is still desirable since it has a relative low cost and can be easily erased and rewritten.
Magnetic tape is typically stored for use in a cassette form. Here, a spool of tape is contained within a housing. When placed on a read/write recording apparatus, a lead end of the tape is advanced across bearings to a take-up reel, and a read/write transducer is located adjacent to the tape in this path. Tape may then be spooled onto the take-up reel and unspooled back into the cassette so that the tape advances in a transport direction across the transducer.
The density of data that can be stored is dependant upon the number of “tracks” which can independently be placed across the width of the tape. Given a standard tape width, data density can increase by increasing the number of tracks. Thus, absent other factors, for data density to increase, the track width must decrease so that a larger number of tracks can be placed on a tape of given width. Currently, tape cassettes have about a four inch reel of tape that is about one-half inch wide. Approximately 320 tracks are placed across the width of the tape. Thus the track width is about twenty-five microns.
At the time of submitting this application, there are various goals in the tape storage industry to increase the storage capacity of a single four inch diameter magnetic tape cassette at least into the range of several terabytes. To accomplish this, track width must be reduced at least by an order of magnitude. While data density is a concern, it is still necessary to access the data quickly and accurately. Typical tape speeds are approximately twelve meters per second across a transducer. Thus, the difficulty of reading a large number of tracks of very narrow track width accurately as such transport speeds becomes a critical issue in this development project.
As should be appreciated by the ordinarily skilled person in this field, it is necessary that the tape head assembly that carries the transducer be highly responsive and controllable. As a tape is transported, deviations in track positioning can result from various conditions. Predominate among these is lateral drift of the tape from a datum reference which can result from tape guide problems, tape flutter, staggerwind on the take-up reel, to name a few. Regardless of the source of the deviation, it is necessary that the transducer maintain an accurate position relative to the tracks at all times. This requires the use of a tape head that can dynamically adjust to tracking deviations with extremely rapid response.
The response time of the tape head is naturally dependent upon the forces which resist the response. Two major forces which can contribute to the response time are the inertia mass of the moving portion of the tape head assembly and frictions inherent in the system that resist such movement. This problem is compounded since the tape head assembly must reciprocate to follow a tape track as the track deviates in either of the two lateral directions. Thus, it is necessary that the movement of the tape head assembly in one direction must be able to be quickly arrested and reversed into the opposite direction at a very high cycle rate.
Current tape head assemblies used in commercial applications employ a carriage that supports a transducer with the carriage mounted on and supported by a guide for translational motion. Typically, these guides are elongated cylinders made, for example, of a ceramic material. Mechanical roller bearings are typically formed as one or more skates which travel along the guide. Such tape head assemblies are marketed, for example, by the Hewlett-Packard Company and by Storage Technology Corporation.
The tape head assemblies noted above can typically weigh between eight and fifteen grams and contain numerous parts. This weight and the various moments of inertia and frictions associated with the mechanical bearings place a limit on the response time of these tape drive heads such that the ability to employ existing tape drive assemblies for use with tape cartridges in terabyte range is questionable. Moreover, these tape head assemblies are expensive to produce and may be subject to costly repairs should a breakdown in the tape head assembly occur.
Accordingly, there is an increasing need in this industry for improved tape head assemblies which may be employed with read/write equipment. There is a need to reduce the complexity of the parts and manufacture of tape head assemblies. There is still a further need for such tape head assemblies that have a minimum mass and which can exhibit extremely fast response times. The present invention is directed to meeting these needs.